Coupling CFD and kMC

This example was presented at theDPG Früjahrstagung 2012 (Munich, 26th March) by Maestri M., Cuoci A., Matera S. and Reuter K., "From atoms to eddies: a novel general approach to chemical reaction engineering".

The atomic-scale understanding of a catalytic process is crucial for the rational understanding and development of catalytic technologies. It passes through the identification of the dominant reaction mechanism, that is an intrinsic multiscale property of the system. This requires efficient and general tools that properly integrate a detailed description of the surface chemistry and the macroscale flow structures. Recently, the new solver CatalyticFOAM has been developed for the first-principles multiscale analysis of catalytic processes. By exploiting the operator splitting technique, it allows for the solution of Navier-Stokes equations for complex geometries for reacting flows at surfaces, based on a mean-field microkinetic descriptions of the surface reactivity. Aiming at a fully first-principles multiscale approach, in this contribution we extend the reliability of CatalyticFOAM beyond the mean-field description of the mesoscale by the incorporation of kinetic Monte Carlo techniques. In this respect, the great challenge is related to the huge difference in the involved time and length scales. To overcome this, we implemented an interpolation technique that efficiently relates the average mass fluxes needed at the macroscale to the microscopic simulations that fully account for the site heterogeneity and distribution at the surface. We tested our approach using the CO oxidation on RuO2 (111) for different reactor configurations and fluid dynamics conditions. Being first-principles at each scale, such a tool represents a crucial step for the first-principles based multiscale analysis of catalytic processes and paves the way towards the rational understanding and development of new reaction/reactor concepts.

 

Operating conditions

Temperature 600 K
Pressure 1 atm
Reactor volume 250 mm3
CO mole fraction 0.66
O2 mole fraction 0.34
Inlet velocity 5 cm/s
Catalyst Ru2O

 

Reactor geometry:

 

Figure 1. Details about the computational domain and the mesh used for the numerical simulations.Figure 1. Details about the computational domain and the mesh used for the numerical simulations.

Calculated results:

Figure 2. Maps of mole fractions of gas species at steady state conditions.Figure 2. Maps of mole fractions of gas species at steady state conditions.

 

Figure 3. Streamlines at steady state conditions.Figure 3. Streamlines at steady state conditions.

 

Figure 4. Profile of CO mole fraction in the inlet mixture.Figure 4. Profile of CO mole fraction in the inlet mixture.

 

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Tutorials

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